Herein, we investigated the correlation between the chemical composition, microstructure, and microwave properties of composites based on lightly Tb/Tm-doped Sr-hexaferrites (SrTb
0.01
Tm
0.01
Fe
...11.98
O
19
) and spinel ferrites (AFe
2
O
4
, A = Co, Ni, Zn, Cu, or Mn), which were fabricated by a one-pot citrate sol-gel method. Powder XRD patterns of products confirmed the presence of pure hexaferrite and spinel phases. Microstructural analysis was performed based on SEM images. The average grain size for each phase in the prepared composites was calculated. Comprehensive investigations of dielectric properties (real (
′) and imaginary parts (
′′) of permittivity, dielectric loss tangent (tan(
δ
)), and AC conductivity) were performed in the 1-3 × 10
6
Hz frequency range at 20-120 °C. Frequency dependency of microwave properties were investigated using the coaxial method in frequency range of 2-18 GHz. The non-linear behavior of the main microwave properties with a change in composition may be due to the influence of the soft magnetic phase. It was found that Mn- and Ni-spinel ferrites achieved the strongest electromagnetic absorption. This may be due to differences in the structures of the electron shell and the radii of the A-site ions in the spinel phase. It was discovered that the ionic polarization transformed into the dipole polarization.
Paper presents the correlation between the composition, microstructure, and microwave properties of composites based on Tb/Tm-doped Sr-hexaferrites and spinel ferrites (AFe
2
O
4
), which were fabricated by a one-pot citrate sol-gel method.
In the ambit of this investigation, we delved into the properties of (Co/Ni)Fe2O4 spinel nanoparticles (CNSNs) with a spectrum of Co/Ni ratios, delineated as Co1-xNixFe2O4, where x adopts values of ...0.0, 0.3, 0.5, 0.7 and 1.0. The synthesis of these CNSNs was adeptly executed via the citrate precursor technique. This study meticulously examined the crystal structure and granular morphology by applying X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was unequivocally determined that each specimen exhibited a homogenous phase. The lattice parameters for the synthesized CNSN compounds agreed with the mean ionic radii of the Co2+ and Ni2+ ions, mirroring their respective concentrations within the nanoparticles. Furthermore, an extensive analysis of the alternating current (AC) electrical properties was carried out, encompassing a broad frequency range from 1 kHz to 3 MHz and a wide temperature range from 303 to 423 K. The observed behavior of the electrical properties was thoroughly evaluated and elucidated, considering the chemical composition of each CNSN. The relationship between the frequency dependency of σac, έ and tanδ is congruent with the prevailing literature and theoretical constructs that elucidate the composite materials' conductivity and dielectric constant, comprising grains and grain boundaries. The present CNSN samples do not exhibit maximum peak for tanδ, potentially due to the wider range of frequencies used than the anticipated peak frequency. The samples' measured conductivity and dielectric constant values displayed a high degree of coherence, corroborating each other's findings. Literature corroborates that the escalation in ac-conductivity values with frequency intimates certainly that the prepared samples may herald promise for utilization in energy storage solutions, bolstering the synergistic efficacy observed. Another conceivable application of these CNSN materials could be their integration in microwave technologies, suggesting a broad scope for future technological advancements.
A detailed study of structural, electric and magnetic properties of FeCo-alloyed nanotubes (NTs) having a different iron to cobalt ratio with an outer diameter of 110 nm and a length/diameter aspect ...ratio of more than 100 was carried out. The nanotubes were produced by electrochemical deposition of metal in the pores of PET film template. Ion-track technology was used to produce templates with cylindrical pores. An increase in the deposition potential from U = 1.5 V to U=2.0 V led to a shift in the atomic ratio of metals in the FeCo alloy from 42 to 51 at.% in favour of cobalt as confirmed by energy dispersive analysis. Analysis of structural features by X-ray diffraction and the selected area electron diffraction revealed that at higher deposition potentials the degree of crystallinity of FeCo NTs increases from a nearly random orientation of crystallites at U=1.5 V to a textured polycrystal at U=2.0 V. This was also consistent with a corresponding increase in electrical conductivity. Based on the analysis of hysteresis curves and Mössbauer spectra, the dominant directions of the texture with respect of the NTs axis were established. An axial magnetic anisotropy and rather high magnetic coercivity (∼ 500 Oe for the orientation with the DC magnetic field parallel to tube axes) were observed and attributed to a dominant contribution of the shape anisotropy with a minor crystal anisotropy term due to the textured growth of the nanotubes. It was shown that the technology of electrochemical deposition in the ion-track template pores makes it possible to synthesize the nanotubes and nanowires with the structural and magnetic properties, which have a high interest with the point of view of a fundamental physics and their technological applications.
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